Fire Detection Apparatus Utilizing A Camera

ABSTRACT

A fire detection device is provided that has a camera that captures a reference image and a measured image. A processor compares intensity of the measured image to intensity of the reference image and uses this comparison to determine if an alarm is generated to indicate the presence of fire. The intensity of the measured image may be the total number of photons of the measured image, and the intensity of the reference image may be the total number of photons of the reference image. In other arrangements, the intensity may be measured between individual corresponding pixels of the reference and measured images.

FIELD OF THE INVENTION

The present invention relates generally to a fire detection device thatemploys a camera and a light for use in detecting fire. Moreparticularly, the present application relates to a fire detection devicethat can be mobile and taken by the user to different locations thatuses an analysis of different frames of the camera to determine whethersmoke is present.

BACKGROUND

Devices for the automatic detection of a fire are valuable because it isimpossible for humans to be aware of their surroundings all of the time.Standard smoke detectors are known and can be one of several differenttypes. For example, photoelectric smoke detectors are known that makeuse of a light beam and a light sensor capable of detecting the lightbeam. When smoke is not present, the light beam shines past the lightsensor and does not contact the light sensor and the alarm is notactivated. However, when smoke fills up a chamber through which thelight beam travels, the light beam engages the smoke and is deflected orscattered some amount resulting in it engaging the sensor and beingdetected by the sensor. The alarm will then activate to warn peoplenearby of the presence of smoke, and hence fire. Other types oftraditional smoke detectors utilize an ionization chamber and a sourceof ionizing radiation to detect smoke.

Fire detection devices are known that capture an image and then analyzethe image in order to determine if flame is present in the image. Onesuch device analyzes an image by looking at the intensity of the red,green, and blue color components of the image. Artificial light in theimage is noted to exhibit only high luminance levels of the redcomponent. These artificial sources of light may be tail lamps andheadlights of vehicles. However, a flame that is present in the imagewill generate high luminance levels of both red and green components. Inthis manner, the fire detection device is able to analyze the colorcomponents of an image to determine if a flame is present, and toexclude other non-flame sources of illumination when detecting the fire.

A different fire detection device that makes use of image processingreceives image data and then sends this image data to a fire detectionmodule for detecting fire or signs of fire. Abstract information fromthe image such as texture, intensity, and color is evaluated. Objectdetection or segmentation is preferably not performed. The system uses acamera mounted onto the ceiling and has a field of view that extendsalong the ceiling but is not pointed downwards to the floor. A blinderor other blocking mechanism is used to prevent the camera from imagingthe floor. This arrangement causes the system to focus only on the areaof the ceiling where smoke will be detected, and to ignore movement onthe floor that would otherwise confuse the system.

Additional fire detection systems have been proposed that seek toincorporate fire detection capabilities into a security system that usesimaging so that two separate systems, security and fire detection, canbe combined into one for cost and utility savings. A beam of light isprojected within the field of view of the camera, and changes in thelight beam brought about by the presence of smoke will be detected bythe system in order to alert the operator of the presence of fire.

There continues to be a need for devices that are capable of detectingthe presence of fire and alerting people in order to provide them withadequate time to escape or put out the fire. Such a device should bemobile so that the user can take it with him or her when traveling andsleeping overnight in places that may or may not be equipped with smokedetectors. As such, there remains room for variation and improvementwithin the art.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended Figs. in which:

FIG. 1 is a side elevation view of a fire detection device located in aroom in which smoke is present at the ceiling of the room.

FIG. 2 is a schematic view of a fire detection device in accordance withone exemplary embodiment.

FIG. 3 is a top plan view of an array of pixels that receive lightduring a reference stage.

FIG. 4 is a top plan view of the array of pixels of FIG. 3 that receivelight during a measurement stage.

FIG. 5 is a top view of the difference of the light intensity of thepixels between the reference and measurement stages of FIGS. 3 and 4.

FIG. 6 is a flow chart showing how the fire detection device detects afire in accordance with one exemplary embodiment.

FIG. 7 is a flow chart showing how the fire detection device detects afire in accordance with a different exemplary embodiment.

FIG. 8 is a plot of the differences detected between the measured imageand the reference image taken over time in accordance with one exemplaryembodiment.

FIG. 9 is a back plan view of a fire detection device as incorporatedinto a smart phone.

FIG. 10 is a front plan view of the smart phone of FIG. 9.

FIG. 11 is a pixel array that shows pixels that are identified andpixels that are not identified.

FIG. 12 is a pixel array that shows an area in which fifty percent ofthe pixels are located that are closer to the center than an area inwhich the other fifty percent of the pixels are located.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

Reference will now be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, and notmeant as a limitation of the invention. For example, featuresillustrated or described as part of one embodiment can be used withanother embodiment to yield still a third embodiment. It is intendedthat the present invention include these and other modifications andvariations.

It is to be understood that the ranges mentioned herein include allranges located within the prescribed range. As such, all rangesmentioned herein include all sub-ranges included in the mentionedranges. For instance, a range from 100-200 also includes ranges from110-150, 170-190, and 153-162. Further, all limits mentioned hereininclude all other limits included in the mentioned limits. For instance,a limit of up to 7 also includes a limit of up to 5, up to 3, and up to4.5.

The present invention provides for a fire detection device 10 that mayemploy a camera 22 in order to detect a fire 92 in a room 12 of abuilding. The fire detection device 10 makes use of a reference imageand then compares subsequent images taken by the camera 22 and comparessame to the reference image to determine whether a fire 92 is present.The fire detection device 10 may identify the presence of fire 92through the identification of the flames themselves, or from smoke 14produced from the fire 92, The fire detection device 10 may have a light24 that illuminates the room 12 to aid the camera 22 in capturing thesequential images. The fire detection device 10 may be incorporated intoa smart phone, cell phone, PDA, or other handheld communication device,or the fire detection device 10 may be a dedicated, stand alone device.Although providing benefit when sleeping in a location that does nothave its own smoke detectors, the hand held device 10 may be used as aback-up device or can be used at any time or location and need not beonly employed when the user is sleeping in other arrangements.

With reference now to FIG. 1, the fire detection device 10 is locatedinside of a room 12 of a building, A fire 92 has started on top of astand 94 in the room 12, and smoke 14 is produced from the fire 92 andhas risen to the ceiling 18 of the room 12. Depending upon the patternof air flow in the room 12, the smoke 14 may or may not flow onto theceiling 18, and may or may not cover all of the ceiling 18. However, itis generally the case that the smoke 14 from a fire 92 will rise andcover some portion of the ceiling 18 and will generally be at thehighest portion of the room 12. The fire detection device 10 is placedon the upper surface of a table 16 that is located inside of the room12. The fire detection device 10 has a light source 24 that emits alight 28 upwards to hit the ceiling 18, The light 28 will illuminate thesmoke 14 as it shines through the smoke 14 to cause particles in thesmoke 14 such as soot and ash to be better visible to the camera 22 ofthe fire detection device 10. The camera 22 has a field of view 26 thatis likewise directed to the ceiling 18 of the room 12 and can moreeasily capture an image of the smoke 14 due to illumination by the light28. It is therefore the case that the light 28 can be located within thefield of view 26 of the camera 22, and that both the light 28 and fieldof view 26 are directed upwards to the ceiling 18. However, it is to beunderstood that in accordance with other exemplary embodiments that thelight 28 and the field of view 26 need not be directed onto the ceiling18. For example, in some arrangements of the fire detection device 10,these elements 28 and 26 may be directed to a wall of the room 12, or tothe floor of the room 12, object in the room 12, to a window of the room12, or to some combination of the ceiling 18, floor, wall, object orwindow.

The camera 22 may be arranged close to the light source 24 so that thereis very little distance between the portion of the light source 24 fromwhich the light 28 emanates and the portion of the camera 22 from whichthe field of view 26 emanates. The distance between these two portionsmay be from 0.1 to 0.4 centimeters, from 0.4 to 0.8 centimeters, from0.8 to 2.0 centimeters, from 2.0 to 2.5 centimeters, from 2.5 to 3.0centimeters, or up to 10 centimeters. In other exemplary embodiments,the distance may be up to 20 centimeters, up to 50 centimeters, or up to1000 centimeters. The camera 22 and light source 24 may be arranged sothat no distance is between them such that a single device provides bothof their functionality. The camera 22 may be arranged so that the fieldof view 26 and the light 28 overlap at some point either during theentire sequence of measurement, or during a portion of the measuringsequence of the device 10. Positioning of the camera 22 and the lightsource 24 close to one another may reduce or eliminate the presence ofshadows that the smoke 14 may cast onto the ceiling 18. Closepositioning of these components may cause the smoke 14 to be morebrightly illuminated by the light 28 so that the camera 22 can pick upthe presence of the smoke 14 as a bright image without the presence of,or minimization of, shadows and darkness caused by the smoke 14, It isto be understood that as used herein the term “smoke” 14 is broad enoughto include ash, soot, burning debris, and any other byproduct ofcombustion caused by a fire 92. The fire 92 may include any type offlame, or may be a smoldering fire that does not necessarily have flamevisible but that does create smoke 14.

FIG. 2 shows the fire detection device 10 in greater detail. The firedetection device 10 may include a housing 20 into which variouscomponents of the fire detection device 10 are housed. All of thecomponents of the fire detection device 10 may be inside of the housing20, or some of the components may be inside of the housing 20 whileother components are located remote from the housing 20 and are notcarried by, and do not engage the housing 20, A light source 24 may beincluded and may be capable of generating a light 28 that is made of asingle beam or multiple beams. The light source 24 may be a flash on acamera in accordance with certain exemplary embodiments, and may be aflash or light on a smart phone in some arrangements of the firedetection device 10. The light source 24 is arranged so that the light28 is not blocked by the housing 20, and portions of the light source 24may extend through an aperture of the housing 20 or the entire lightsource may be located outside of the housing 20 and not covered by thehousing 20.

A camera 22 is carried by the housing 20 and may likewise be completelylocated outside of the housing 20, completely inside of the housing 20,or partially inside and outside of the housing 20. The camera 22 may becompletely inside of the housing 20, and a lens of the camera 22 mayreceive light from outside of the housing 20 via an aperture thatextends through the housing 20. An internal timer and control 30 may bein communication with both the camera 22 and the light source 24 inorder to send instructions to both in order to tell both when and how toactuate. For example, the light source 24 may be instructed to flash oneor more times in sequence and the intensity and length of each of theflashes may be ordered by the internal timer and control 30, In asimilar manner, the camera 22 may be instructed by the internal timerand control 30 as to when to capture an image, whether to focus or notfocus, what shutter speed to use, whether to take a color or black andwhite image, and whether to take video footage or still images. Thecamera 22 may be instructed by the internal timer and control 30 tomanipulate the flash intensity of the light source 24 so that the device10 may function in a dark room without producing too much light thatwould be a nuisance to someone trying to sleep. The flash intensitycould also be varied or controlled in other situations as needed ordesired by the device 10. The internal timer and control 30 may becapable of instructing the camera 22 and the light source 24 to recordan image that is illuminated when the light source 24 lights so that thepicture is timed with the flash. Information or instructions from thecamera 22 may be communicated to the internal timer and control 30, Thefire detection device 10 may thus be capable of adjusting the shutterspeed, image focusing, light to flash, and other variables associatedwith the camera 22.

The fire detection device 10 may also include an internal image memory32 that receives information from the camera 22. The image data may becompletely digital in certain exemplary embodiments such that no analogimage data is received or used at all by the fire detection device 10 atany point from the light entering the lens of the camera 22 onward. Theimage data can be stored in the internal image memory 32 and may betransferred to a processor 34 of the fire detection device 10. In asimilar manner, the processor 34 may communicate with the internal imagememory 32 in order to instruct the internal image memory 32 to docertain things such as sending or removing data within the internalimage memory 32.

The processor 34 may have various modules that perform differentfunctions. For example, the processor 34 may have a camera and flashmodule 36 that sends information to and receives information from theinternal timer and control 30. The camera and flash module 36 may bepart of an algorithm that controls the fire detection device 10 andcauses it to function to detect the fire 92. The camera and flash module36 may send signals to the internal timer and control 30 to cause it togenerate light 28 and the camera 22 to capture the image. Likewise,particulars about the light 28 and the camera 22 can be sent to thecamera and flash module 36 via the internal timer and control 30 toinform the module 36 when pictures are being taken and when the light 28is being emitted.

The processor 34 may also include an image comparator module 40 that canreceive information from the internal image memory 32 that can comparethe different images to one another or to a reference image. Thesecomparisons can be sent to an image analyzer module 38 that can analyzethe various comparisons in order to determine if a fire 92 is takingplace or is not taking place. The image comparator 40 may send andreceive information to and from the camera and flash module 36 and theimage analyzer 38. If the image analyzer module 38 determines that afire 92 is taking place, the image analyzer module 38 may send a commandto an alarm module 42 that in turn causes an alarm to be generated bythe fire detection device 10. The alarm may be a sounds alarm, avibration alarm, or a visual alarm or may include any combination of thethree. Additional alarm types are possible in other exemplaryembodiments, and the fire detection device 10 can generate any type ofalarm for informing the user that a fire 92 is taking place. Forexample, the alarm can be the sending of a message, such as a telephonecall, text message, email, or other message, to a 911 emergency center,a fire department, a hotel front desk, or a monitoring serviceassociated with the device. The alarm module 42 need not be present inother arrangements. Instead, the image analyzer module 38 of theprocessor 34 may cause the alarm to be directly generated such that thefire detection module 10 makes a sound, vibration, and/or visual warningto signal an alert of a fire 92.

The camera 22 may be a digital camera that directly samples the originallight that bounces off of the subject of interest (smoke 14 or ceiling18) and that breaks the sampled light down into a series of pixelvalues. The light 28 is used to illuminate the smoke 14 to image thesmoke 14, and the light 28 itself is not analyzed as a beam. The digitalcamera 22 may include a series of photosites (pixels) that each detectthe amount of incident light (number of incident photons) and store thatas one electron charge per detected photon. The amount of charge in eachpixel is subsequently converted into a proportional digital count by anA-to-D converter. The number of photons of light that are imparted ontoeach photosite thus may be counted and this number may in turn be usedto represent the intensity of the light striking that particularphotosite. In this manner, the amount of light striking each pixelelement on the surface of the camera 22 can be measured and analyzed. Inthis application, we refer to the camera digital output generally as“photons”, “photon count”, “light intensity”, or “digital count”interchangeably.

With reference now to FIG. 3, a pixel array 66 of the camera 22 is shownin which twelve pixels are illustrated. In reality, the pixel array 66can be composed of millions of pixels and thus it is to be understoodthat the pixel array 66 illustrated is greatly simplified for sake ofdiscussion relative to the fire detection device 10.

The camera 22 may be, for example, an 8-bit device in which lightintensity values are digitized from 0-255. Alternatively, the camera mayhave 12-bit or greater precision, or may be a color camera producing,for example, 24-bit RGB data. For purposes of illustration, 8-bit datais assumed. A digital count of 20 may correspond to a few hundredphotons, A light intensity of 21 is higher than a light intensity of 20and thus represents more photons than a light intensity of 20. It is tobe understood that the numbers used herein are only exemplary indescribing one or more embodiments of the device 10. The first pixel 68is shown as having a light intensity of 20. In other words the photonscaptured by the first pixel 68 in the image obtained by the camera 22are represented by a digital count of 20. As stated, it may be the casethat several hundred photons were in reality captured to produce thecount “20.” The number 20 is simply used for sake of convenience and inaccordance with standard optical practices in some known devices. Thesecond pixel 70 is located next to the first pixel 68 and has a lightintensity of 10 which also is the number of photons captured by thesecond pixel 70 when obtaining the image. The additional pixels aredesignated as the third pixel 72, fourth pixel 74, fifth pixel 76, sixthpixel 78, seventh pixel 80, eighth pixel 82, ninth pixel 84, tenth pixel86, eleventh pixel 88, and twelfth pixel 90 and all likewise have aparticular light intensity measurement value that is shown within theirrespective boundaries. Again, as previously stated the actual number ofphotons may be of course greater than 10, 40, 70, etc., but are listedas being these numbers for sake of example, and in accordance withoptical imaging standards. The fire detection device 10 may capture animage and designate this image as a reference image. The pixel array 66of FIG. 3 may be an example of the reference image captured by the firedetection device 10. As previously mentioned the image comparator module40 may obtain this image and designate it as the reference image.

The camera and flash module 36 may cause the internal timer and control30 to obtain another image by actuating the camera 22 and the lightsource 24 at some point in time after the reference image is obtained.This time may be from 1 to 3 seconds, from 3 to 6 seconds, from 6 to 10seconds, or up to 1 minute of time. FIG. 4 shows the photo array 66 ofFIG. 3 some amount of time after the reference image of FIG. 3. Thephoto array 66 of FIG. 4 may be identified as a measured image. Theimage that is measured at the measured image may be different in somerespects from the image that is measured in the reference image. Asshown in FIG. 4, the image has changed in that the first pixel 68 nowhas a measured light intensity of 10 instead of 20 from that in FIG. 3.As a fewer number of photons have been captured by the first pixel 68during this image, it means that the image is darker in this portion inthe measured image than in the reference image. The second pixel 70 hasa measured value of 10 which is the same as that of the second pixel 70in the reference image of FIG. 3, and this signifies the fact that theimage has not changed at all between the reference and measured imagesat the second pixel 70.

Other pixels in the measured image of FIG. 4 show an increase in lightintensity that signifies the image is brighter at those pixels in themeasured image than in the reference image. For example, the seventhpixel 80 went from an intensity of 100 to 150, and the twelfth pixel 90went from an intensity of 130 to 200. FIG. 5 shows a difference image inwhich the pixel array 66 is again displayed. The difference image may bean image generated by the fire detection device 10, or may simply be acomputation of a portion of the fire detection device 10 such as the bythe image analyzer 38. The difference image of FIG. 5 shows the lightintensity of each pixel that is calculated by taking the measured lightintensity of that particular pixel minus the reference light intensityof the same pixel. For example, the first pixel 68 has a differencevalue of −10 because the first pixel 68 went from a reference value of20 to a measured value of 10. The seventh pixel 80 has a differencevalue of 50 (150-100), and the twelfth pixel 90 has a difference valueof 70 (200-130). The various differences in all 12 pixels are shown inFIG. 5, and this difference image, if displayed by the fire detectiondevice 10, can be arranged so that positive difference values are whiteand negative difference values are black. The difference image can bedisplayed such that if the difference is positive, the pixel in questionis white, and if the difference is negative the pixel is blackregardless of the intensity level. In other arrangements, the pixel canbe displayed darker or lighter based on the measured intensity level ofthe pixel in question.

The previously described assignment may include a camera 22 and array 66that is black and white. The setting of the camera 22 may be a black andwhite setting, or the camera 22 may only be capable of obtaining blackand white photographs. In other arrangements, the images captured by thecamera 22 can be color images, Here, red, blue, and green components canbe captured and held in the pixel array 66. The color or RCB image canbe converted by an algorithm into a luminance image and processed in asimilar manner as described with respect to the black and whitecapturing and processing method.

As shown in FIG. 5, some of the differences are positive, some negative,and some unchanged between the reference image and the measured image,Changes that denote an identifiable change in the image are generallyclustered around a set of pixels that are contiguous or at least closeto one another. For example, the seventh pixel 80, eighth pixel 82,eleventh pixel 88, and twelfth pixel 90 all show significant brightnessin the measured image as compared to the reference image. These pixels80, 82, 88 and 90 are all contiguous or at least close to one another.The significant increases in these close/contiguous pixels 80, 82, 88and 90 may indicate that a bright item, such as smoke 14, is detected.When smoke 14 is detected the alarm may sound because the fire detectiondevice 10 associates the presence of smoke 14 with the presence of fire92.

The fire detection device 10 may be arranged to detect the presence ofsmoke 14 by only using the intensity of light imparted onto the pixelarray 66, and not color that is perceived by the camera 22 or any otherpart of the fire detection device 10 such as the processor 34 or theinternal image memory 32. However, it is to be understood that theanalysis as to whether smoke 14 is or is not present may in fact includeconsideration of the color information obtained from the observed image.

FIG. 6 shows an analysis of the fire detection system 10 that can beused in order to ascertain the presence of smoke 14 or flames from afire 92. The analysis may be an algorithm that is executed by theprocessor 34, or a combination of different processors. The analysisfirst commences with the establishment of a threshold that is based uponthe measurement of one or more reference frames. Even if the image doesnot change, the camera 22 will probably never register the sameintensity on all of the pixels in the pixel array 66 as successiveimages are taken. This is because vibrations on the table 16,temperature changes, and camera 22 properties all function to createnoise in the image capture process. For instance, the camera 22 may havean autofocus, or other mechanical processes, that causes movement andhence variation in brightness observed in the same image betweensuccessive frames. As such, it is expected that there will be somenaturally occurring noise in the system and the fire detection device 10may be arranged to alert taking the presence of this noise into account.The autofocus may be turned off in certain arrangements so that theanalysis is performed without the image taken by the camera 22 in focus.In other arrangements, the image may in fact be in focus, and theautofocus feature of the camera 22 may be used. Even beyond thesereasons for variation, the camera 22 may never register the sameintensity on all of the pixels in the pixel array 66 from successiveimages taken because any photon counting process is inherently astochastic process and the values may be different from successiveimages even without any scene change between successive images.

In step 96, a first reference frame 1 is taken by the camera 22. Asecond reference frame 2 some amount of time later may then be taken bycamera 22 at step 98, The comparison function previously describedbetween the pixel arrays 66 of the first and second reference frames maybe conducted at analysis step 100. The difference between the frames canbe calculated as a total difference in intensity between the first andsecond reference frames. As such, the total number of photons from thefirst frame can be subtracted from the total number of photons from thesecond reference frame to arrive at this difference. Given the nature ofthe photon counting detection device, the =distribution of each pixel inthe pixel array 66 would be considered to be Poisson. The differencesbetween each pixel from the first to the second reference frame would bedistributed as a Skellam distribution. It is to be understood, however,that this distribution need not be a Skellam distribution in otherarrangements. For instance, if a fan or some other movement were withinthe field of view 26, a Skeliam distribution would not be expected. Thedistribution of pixels in these cases may be estimated empirically byusing a few images in which the assumption is made that the scene isstable. This estimated distribution may be used instead.

From this at step 100, the threshold could be set up beyond which alikelihood of observing a pixel difference is low. In one example, forinstance, the reference threshold frame 1 photon count at step 96 may be1 million photons, and the reference threshold frame 2 photon count atstep 98 may be 1.2 million photons and the difference may be 0.2 millionphotons. The threshold in step 100 may be established at 1.5 millionphotons based upon analysis of the reference threshold frames, in whichthe difference was 0.2 million photons and the threshold is establishedas 0.3 million photons thus meaning the threshold is 1.5 million photonsfrom the frame 2 reference frame. Although described as taking only tworeference threshold frames, it is to be understood that this is only forsake of example and that multiple reference frames can be measured andused in arriving at the threshold set at step 100. The threshold may bethe same for the entire time the fire detection device 10 functions uponstart up, or the threshold may be adjusted by taking different referenceframe measurements to result in the establishment of new thresholds atdifferent times through the process.

The process may then move onto step 102 in which a measured image iscaptured. The camera 22 can take a measurement image of the ceiling 18or other area of the room 12. The successive measurements may be takenevery second, every two seconds, or every three seconds. In otherarrangements, from 3-5, from 5-30, or up to 120 seconds may take placebetween successive measurements, Once a measured image is captured bythe camera 22, at the next step 104 the measured image is compared to aprevious reference image. The reference image may be the one taken inreference frame 1, or may be a reference image that is updated atvarious intervals through the measurement process. For example, thereference frame can be updated every 5 minutes, every 10 minutes, orevery 15 minutes as the fire detection system 10 functions. Thereference image may be the same image as the reference frame 1 image, ormay be the same image as the reference frame 2 image in accordance withcertain embodiments.

The comparison at step 104 may be performed in the manner previouslydiscussed with reference to FIGS. 3-5 in which the total number ofphotons of the pixels that are different are determined. For instance,the reference frame may have 1 million photons and the measured imagemay have 1.6 million. The difference is 0.6 million photons which isgreater than the established threshold of 0.3 million photons (or totalnumber of 1.5 million photons).

The presence of smoke 14 may cause the image to be brighter and henceadditional photons will be present when smoke 14 is present. The smoke14 may cast a shadow onto the ceiling 18, and cause dark areas and hencefewer photons, but the close placement of the camera 22 to the lightsource 24 may minimize or eliminate the presence of shadows cast by thesmoke 14. The evaluation may only look towards an increase in the numberof photons between the measured and reference images and may ignore anydecreases. However, it is to be understood that both increases,decreases, and no changes are considered in accordance with variousexemplary embodiments.

The output of the image comparator 40 and image analyzer 38 modules willbe a detection statistic, as shown in FIG. 8. This may be as simple asthe summed pixel values of the difference image, or a more robust indexsuch as the (a) root-mean-square difference (RMSD), (b) summed absolutevalues of differences, or (c) a more complex measure that includes thenumber of contiguous pixels above threshold in the difference image, orthe RMSD of contiguous pixels that deviate up or down by more than athreshold value in the difference image. The detection statistic can becalculated in a variety of manners in accordance with differentexemplary embodiments, and some of these manners are described in thisapplication at other portions of the application.

FIG. 8 shows a plot of the detection statistic that in this embodimentis the difference between the number of photons in the measured imageminus the number of photons in the reference image on the Y-axis versustime on the X-axis. In the example illustrated in FIG. 8, the thresholdis set at approximately 60,000 photons which is the difference betweenthe measured minus the reference. Continuous measurement occurs as timeincreases on the X-axis in which the difference between the total numberof photons in the measured image minus the total number of photons inthe reference image is plotted. As shown, at around 52 seconds of time,the detection statistic crosses over the established threshold. Theanalysis at this point may then move onto additional comparisons as willbe momentarily discussed in order to determine whether to sound thealarm. It is to be understood that the plot of FIG. 8 need not begenerated or displayed during the running of the fire detection system10 in certain embodiments.

With reference back to Hg. 6, if the threshold is not exceeded in step104, the process moves back to step 102 and the next image is measuredand then subsequently reevaluated in step 104. If the threshold is infact exceeded in step 104, the system moves on to step 106 in which thepixels of the pixel array 66 are checked in order to determine if theyare greater than some number. For example, the system may determinewhether 10% or more of the pixels in the measured image have anintensity that is greater than their respective intensities in thereference frame 1. This calculation will be on a pixel by pixel basisand will not be a composite comparison of the intensity of all of thepixels in frame 1 verses all of the pixels in the measured image.Additionally or alternatively, the system may at step 106 determinewhether all of the pixels in the measured image have a greater intensitythan they did in the reference frame 1. Additionally or alternativelythe system may measure at step 106 whether the threshold was exceeded by10% or fewer of the pixels of the pixel array 66. All three or one of,or any combination of the aforementioned measurements may be taken atstep 106 in order to determine whether the pixels are greater than somenumber. It is to be understood that the percentages mentioned are onlyexemplary and that others are possible in accordance with otherexemplary embodiments.

Although not shown in the flow chart, an additional step may be presentat this point of the process. This additional step may involve thecamera 22 capturing additional reference frames at a faster pace, thatis at shorter intervals of time between frames, than what was capturedin the earlier steps 96 and 98. These additional frame captures atshorter time intervals may give additional measurements with which to domore calculations for more precise results. The additional measurementsmay be used to validate the previously described check at step 106, andif validated the method may go on to step 108. If not validated, themethod may be back to step 102. As previously stated, this additionalstep may be optional and need not be present in other arrangements ofthe device 10.

If the analysis determines at step 106 that the pixels are not greaterthan some number, the analysis moves back to step 102. However, if thelimit that was established in step 106 is in fact exceeded the processmoves on to step 108. Here, location considerations of the pixels fromstep 106 are taken into account. The location considerations are basedupon which specific pixels of the pixel array 66 are identified in step106. In step 108 the processor 34 may determine whether the pixelsidentified are contiguous or are spuriously spaced and thus separatefrom one another. This determination may function to help the device 10decide whether smoke 14 is present because the identified pixels may betouching if smoke 14 is present and may not be touching if it is notpresent. In some arrangements, the processor 34 may determine whethergreater than fifty percent of the pixels that have increased photonintensity are contiguous. In this regard, greater than 50 percent of theidentified pixels are immediately adjacent another identified pixel. Inother embodiments, the number may be 60 percent, 70 percent, or up to 90percent.

With reference now to FIG. 11, a pixel array 66 is illustrated in whichsix of the pixels are identified pixels, and thus are identified ashaving increased photon intensity. These six pixels are the first pixel68, the second pixel 70, the fourth pixel 74, the fifth pixel 76, thetenth pixel 86, and the twelfth pixel 90. The first pixel 68, secondpixel 70 and fifth pixel 76 are all contiguous because both the secondpixel 70 and the fifth pixel 76 border on and engage the first pixel 68.However, the fourth pixel 74 and the twelfth pixel 90 are not contiguousbecause there are not pixels that are located immediately adjacent themthat are likewise designated as identified pixels. The tenth pixel 86may contiguous in some exemplary embodiments because it is locateddiagonally across from the fifth pixel 76 and thus may be referred to ascontiguous. However, in other embodiments of the system the tenth pixel86 is not contiguous because the spatial orientation of the tenth pixel86 is diagonally arranged with respect to the fifth pixel 76 and this isnot considered to be contiguous.

Additionally or alternatively, the system at step 108 may seek todetermine whether the identified pixels are near the edges of the pixelarray 66, This may be indicative of smoke 14 invading the field of view26 of the camera 22 because smoke 14 will first appear at the edges ofthe pixel array 66 and not at the center of the pixel array 66. Thisdetermination may signify whether a “cloud” of smoke 14 is moving intothe field of view 26 from a corner or edge. Still additionally oralternatively in step 108, the processor 34 in step 108 may seek todetermine whether the number of identified pixels is large enough. Here,it may be necessary for the pixels that are identified in step 106 tofill in a certain sized area of the pixel array 66, and if they do notthen this space requirement of the analysis is not met. In somearrangements, the system may determine whether all or a majority of theidentified pixels are located in a region of the pixel array 66 thatincludes half of the pixels of the pixel array 66 that are farthest fromthe center of the pixel array 66. In other words, the pixels that arefarthest from the center of the pixel array 66 are not the fifty percentof pixels that are closest to the center. If the pixel array 66 isrectangular, the fifty percent of closest pixels may be shaped as arectangle with the center of the pixel array 66 at its center. The fiftypercent of pixels farthest from the center may form a picture frame likeborder about the pixels that are included as the ones in the closestfifty percent. If all, 75% or greater, 65% or greater, 50% or greater,or 35% or greater of the identified pixels fall within the fifty percentof pixels specially located farthest from the center of the pixel array66, the system may determine that the space analysis is confirmed forsmoke 14.

FIG. 12 shows a pixel array 66 but leaves out the pixels for sake ofclarity. The pixel array 66 is square shaped, and the pixels maylikewise each be in the shape of a square. A center 132 of the pixelarray 66 is noted, along with all four of the edges 134 which make upthe outer boundary of the entire pixel array 66. A center area 128 ofthe pixel array 66 is the area in which fifty percent of the pixels ofthe pixel array 66 are closest to the center 132, This center area 128may be circular in shape. An outer area 130 of the pixel array includesfifty percent of the pixels of the pixel array that are farthest fromthe center 132 along any radius from center 132. All pixels in the outerarea 130 are more distant along any radius from the center 132 than anypixel in center area 128, The outer area 130 includes the pixels of thepixel array 66 that are generally closest to the edges 134. In someexemplary embodiments, the system may determine whether some number ofthe identified pixels are in the outer area 130, and if so may cause thespace requirement of the system to be met. This number may be 100%, 90%,80%, 50%, or from 50%-85% in certain exemplary embodiments. Alternately,the system may look at the number of identified pixels that are in thecenter area 128 and may use this information to determine whether thespace requirements of the system are or are not met.

The space analysis in step 108 may employ one, two or any combination ofthe aforementioned comparisons in order to determine whether the spacerequirements are met. If this is the case the process will move on tostep 110 in which an alarm is triggered to alert the user that smoke 14is present and thus a fire 92 is present. If the space evaluation of theidentified pixels is not determined to be in the affirmative, then thesystem realizes that no smoke 14 is present and moves once again back tostep 102 to continue capturing measurement images. The fire detectiondevice 10 will function for a preset time, or until it is turned off bythe user.

The analysis may be different in accordance with other exemplaryembodiments of the fire detection device 10. FIG. 7 shows a differentanalysis of the fire detection device 10 for detecting smoke 14 and fire92. The analysis starts at step 112 in which a reference frame is taken,Here, the intensity of each pixel of the pixel array 66 is individuallymeasured. For instance, the first pixel 68 may be measured as being 20photons, the second pixel 70 as being 10 photons, and so on. At step114, a second reference frame 2 is taken and the same pixels 68 and 70are again measured, Here, pixel 68 may be 22 photons, and the secondpixel 70 may be 12 photons. The remaining individual pixels of the pixelarray 66 are likewise measured at the second reference frame 2.

Moving on to step 116, the threshold is established by setting athreshold for each individual pixel of the pixel array 66, Thisthreshold may be set by any statistical process, such as thosepreviously described with respect to steps 96, 98, 100 above. Forinstance, the threshold for the first pixel 68 may be set at 24 photonsbased upon a statistical analysis of the levels between the first andsecond reference frames. The additional pixels of the pixel array 66 maylikewise have their own thresholds set which may be different than thethreshold of the first pixel 68. The threshold of the second pixel 70may be 13.

The system may move on to the next step 118 after establishing thethresholds and take images in sequential fashion as the fire detectiondevice 10 continuously monitors the room 12. The timing betweensuccessive images may be performed as previously discussed. The systemanalyzes the measured image at step 120 in which the measured pixel iscompared to a reference pixel. The reference pixel may be the intensityof the first pixel 68 at the reference frame in step 112 or 114, or maybe a reference pixel that is measured at various timing points throughthe monitoring. At the comparison step 120 the intensity of the firstpixel 68 of the measured image is subtracted from the intensity of thefirst pixel 68 at the reference image and this difference is compared tothe threshold of the first pixel 68 established at the threshold step116. For instance, if the threshold is 24 photons and the intensity ismeasured as being 25 photons then the threshold is exceeded and thefirst pixel 68 is identified as having an exceeded threshold at step120. The second pixel 70 may be measured as having an intensity of 15and this number may be above the threshold of 13 that was previously setfor the second pixel 70. All of the pixels of the pixel array 66 may besimilarly evaluated at step 120 to determine which ones are above theirthreshold.

The process may then move to step 122 in which a determination is madeas to whether the number or percentage of pixels that have exceededtheir threshold is above some set number or percentage. For example, theset number may be 40,000 pixels, or may be set at 10%. The set number orpercentage may be established independently from the thresholdcalculation at step 116, or may be established based in whole or in parton the values established at the threshold step 116. The number may beselected as being anywhere from 30,000 to 100,000 pixels, from 100,000to 500,000 pixels, from 500,000 to 2,000,000 pixels, or up to 5,000,000pixels. It is to be understood that the aforementioned numbers of pixelsare only exemplary and that others can be used in accordance withdifferent exemplary embodiments. If this number/percentage is notexceeded at step 122 then the system moves back to step 118 to continuetaking image measurements. If the number/percentage set for the pixelshas in fact been exceeded then the process moves on to step 124.

At step 124, the pixels that were determined to be over their respectivethresholds at step 120 are evaluated in order to ascertain location andspacing information. This analysis would be the same as described abovewith respect to step 108 in that the number of the pixels, whether theyare contiguous, and whether they do or do not emanate from an edge orcorner of the pixel array 66 is looked at to determine if the pixels areindicative of smoke 14 or fire 92. If the pixels that are over theirthresholds do satisfy space or size requirements then the systemtriggers the alarm at step 126. If not, then the system moves back tostep 118 for continued monitoring. Again, one or any combination of thevarious space considerations can be taken into account to determinewhether the space requirements at step 124 are met.

It is to be understood that the previously described methods of analysiscan be modified in other embodiments. For example, the spacerequirements in steps 108 and 124 can be eliminated in somearrangements. In other embodiments, the comparison steps 104 and 120 maycompare only the top 10% of pixels based upon their photon count so thatthe 90% of pixels in the image that have the lowest pixel count wouldnot be evaluated at all. This top 10% of pixels would be the onesidentified as being the top 10% in the measurement steps 102 and 118.

The previous arrangements have been described with detection of smoke 14associated with additional photons being detected by the pixel array 66.However, the photons associated with smoke 14 detection need not alwaysbe in the positive, or addition of photons, but could be associated withthe removal of photons. For example, shadows cast by the smoke 14 ontothe ceiling 18 or other surfaces, or the presence of black smoke maycause the image that is measured to be darker than the reference image,and hence fewer photons detected by the fire detection device 10. Inthis regard, the fire detection device 10 may also have an analysis thatlooks for the loss of photons in basically the same manners aspreviously discussed with respect to the increase in photons.

The thresholds mentioned may include an upper level and a lower level.The upper level may be associated with an increase in brightness of thepixel, and the lower level is associated with a decrease in brightnessof the pixel. If the pixel of the measured image has an intensity higherthan the upper level, then the threshold is exceeded. Likewise, if thepixel of the measured image has an intensity lower than the lower level,then the threshold is exceeded. The threshould as described herein maythus have upper and lower limits so that if the measured image isoutside of these limits, the threshold is deemed exceeded. Stillfurther, or alternatively, the fire detection device 10 can be arrangedso that it looks for changes in the absolute values of photons in themeasured images with respect to the reference image. The use of absolutevalues may be able to take into account both increases and decreases oflight intensity caused by the smoke 14. Also, the analysis when usingabsolute values can be similar to those described above that look forbrightness in the measured image versus the reference image.

However, although described as taking all positive and negative changesof the photons into account when seeking to identify smoke 14, somearrangements of the fire detection device 10 only take positive changesinto account. In this regard, any negative change between the referenceframe and the measurement frame is ignored and plays no part intowhether the analysis does or does not detect smoke 14, Only positivechanges count. The positive changes are associated with an increase inphotons from the reference frame to the measurement frame and thus onlyan increase in brightness is looked at to determine whether smoke 14 isor is not present. The thresholds in these arrangements may thus haveonly an upper limit, since a decrease in photon count would be ignoredanyway.

The fire detection device 10 can be a stand-alone device in that thedevice functions to detect smoke 14 and fire 92 but does not perform anyother functions. Alternatively, the fire detection device 10 may beincorporated into another device that is capable of performing otherfunctions. For example, the fire detection device 10 may be incorporatedinto a cell phone, smart phone, personal digital assistant, or laptopcomputer. With reference now to FIG. 9, the back surface of a firedetection device 10 is shown that is incorporated into a smart phone.The smart phone has a housing 20 that may be a case into which the smartphone is stored, or may simply be the original housing provided with thesmart phone. The processor 34 can be a processor of the smart phone, ormay be a processor of a computer remote from the smart phone. The camera22 and the light source 24 of the smart phone are shown, and may be thecamera 22 and the light source 24 that is used by the fire detectiondevice 10 when monitoring for smoke 14, The smart phone is placed ontothe upper surface of the table 16 so that the camera 22 and the lightsource 24 are directed upwards to the ceiling 18 and so that the screen44 of the smart phone is blocked from view by being positioned facingthe upper surface of the table 16 onto which the smart phone is placed.The smart phone may include volume buttons 50 and 52, and a power button48 for turning the smart phone on and off.

FIG. 10 shows the front side of the smart phone of FIG. 9 in which thescreen 44 displays information relevant to the fire detection device 10.The analysis portion of the fire detection device 10 may be anapplication, or app, that is downloaded onto the smart phone orotherwise available to the smart phone. The app may control the camera22 and the light source 24 and can process the information obtained inorder to determine whether an alarm should be sounded. If so, the appmay instruct the speaker of the smart phone to emit an audible warning,the screen 44 of the smart phone to emit a visual warning, or vibrationof the smart phone to activate in order to alert the user that a fire 92is taking place, Although described as alerting directly at the firedetection device 10, the alarm may be a phone call, text message, orother communication sent over a wired or wireless network to one or moremonitoring stations, such as a fire department or a police station. Thealarm may be sent to other devices remote from the fire detection device10 in certain arrangements. The alarm may be sent to any designatedindividuals or entities such as fire departments, EMS, or police.

The smart phone may have a physical button 54 located on the front faceof the smart phone that is used to control certain features of the smartphone and to provide input. The smart phone includes a second camera 46that can likewise be used to capture images. In this regard, the smartphone could be placed on its back side so that the screen 44 and thesecond camera 46 point upwards towards the ceiling 18, and away from theupper surface of the table 16. The fire detection device 10 may functionso that the second camera 46 acquires the necessary images. A secondarylight source 24 may be present as a different device from the smartphone that may be controlled by the smart phone or not controlled by thesmart phone. The screen 44 may provide sufficient illumination so as tofunction as the light source 24. In yet other arrangements, the firedetection device 10 does not employ a light source 24 and may take theimages and prepare the analysis without the use of light 28 generated bythe fire detection device 10.

The app that may be included in the fire detection device 10 may presentcertain information on the screen 44 to inform the user of thefunctioning of the fire detection device 10, and to request informationfrom the user to help the fire detection device 10 identify fire 92. Atitle 56 of the application can be displayed on the screen 44 in orderto inform the user that the smart phone is functioning in fire detectionmode. The screen 44 may also present the user with a start-up screen 58that informs the user that the fire detection device 10 is in is thestartup mode. The start-up screen 58 may inform the user that the firedetection device 10 has not yet started imaging the room, and mayrequest input from the user in order obtain information that may betterhelp the fire detection system 10 in determining whether a fire 92 ispresent.

The start-up screen 58 may request the user enter a first setting 60that can ask the user whether a ceiling fan is or is not turned on inthe room when the fire detection device 10 is functioning to check for afire 92. The user can use the smart phone to enter a yes or no answer,and the fire detection device 10 can adjust its sensitivity according towhether a ceiling fan is running. The presence of a running ceiling fanmay contribute to variations in the lightness and darkness sensed duringmonitoring.

The start-up screen 58 may also have a second setting 62 that asks theuser whether the blinds to the room are open or closed, Open blinds maycause light from the outside to enter the room, and associated movementand shadows may be present within the room that could be imaged by thecamera 22. The fire detection device 10 may be programmed with differentsensitivity depending upon whether this movement is or is not to beexpected in view of the fact that light and other non-fire relatedmovements can be present in the room if the blinds are open. Anotherthird setting 64 may further be presented to the user at the start-upscreen 58 which asks the user how long the fire detection device 10should function in fire detection mode. If the user plans on getting upat 6:00 am, power can be saved by shutting off the fire detection modeat this time, or if movement in the room is expected by the user turningon lights and so forth at 6:00 am then the frequency of false alarms canbe minimized or eliminated if the fire detection device 10 is not usedwhen it is not needed.

The fire detection device 10 may be a mobile device that the user cantake with him or her to different locations. For example, the user canutilize the fire detection device 10 at different locations whentraveling at such times and locations the user needs to sleep. The firedetection device 10 may be designed so that the camera 22, light source24, and processor 34 are not mounted to a table 16, floor, wall or othersurface in a room 12 but are instead separate from such surfaces and notattached. In other arrangements, the fire detection device 10 may infact be an installed device that is in fact attached to a floor, table,or other surface in a room 12.

The fire detection device 10 may use a camera 22 that is additionallyused as a security camera to monitor a room 12, hallway, parking lot, orother location. Images from the camera 22 may thus be used not only todetect fire 92, but to monitor for intruders or other activity. The firedetection device 10 may thus be incorporated into an all ready existingsecurity system. In yet other arrangements, the fire detection device 10may include some components of a desktop computer. For example, a camera22 could be incorporated into a desktop computer and used to captureimages. The processing of the images may be done by the desktop computeror may be sent to a remote location for processing. The alarm 42 may besounded at the desktop computer, or may be sounded at a location remotefrom the desktop computer. As such, in some arrangements the camera 22may be mobile in that it is incorporated into a device that by nature ismoved from place to place, or the camera 22 may be static in that itremains in a single location. In the instance where the camera 22remains in a single location, it may be rigidly positioned such that itis incapable of moving, or may be capable of being panned and tilted sothat different fields of view 26 are possible.

The fire detection device 10 can be employed at facilities such asconcert halls, movie theaters, factories, and traffic tunnels to detectfire 92. Still further, the fire detection device 10 may also be used todetect smoke 14 from cigarettes in locations like resturants andairplanes that prohibit smoking. The fire detection device 10 can beemployed in any location in which one desires a determination as towhether fire 92 is or is not present.

The fire detection device 10 as used herein may be capable of detectingsmoke 14 and then sounding the alarm because the presence of smoke 14indicates that a fire 92 is present, Additionally, the fire detectiondevice 10 may also be capable of detecting the flame produced by fire 92in order to determine that the fire 92 is present. The aforementionedprocessing steps can be set up to check for brightness associated with aflame of the fire 92 and can sound an alarm if there is a flamedetected.

In still further arrangements, the fire detection device 10 is capableof detecting smoke 14 of the fire 92, but cannot and is not capable ofdetecting the actual flame of the fire 92. The fire detection device 10may alert that something is happening, flame, without even detectingflame. An alarm may thus be given even though the actual item detectedis not even recognized or seen by the device 10. The fire detectiondevice 10 may not take texture or color of the image into account whendetermining whether smoke 14 is present. In certain arrangements, thefire detection device 10 may only look at intensity of the pixels andlocation of the pixels relative to the pixel array 66 when looking forsmoke 14. In some embodiments, the fire detection device 10 may look forspecific properties of smoke 14 and alert based on these properties. Forinstance, the device 10 may look for how smoke 14 moves across a room 12in order to determine whether smoke 14 is or is not present whenanalyzing the captured images. It is to be understood that as usedherein, such as in the specification and claims, that the detection offire 92 can be inferred from the detection of smoke 14 such that thealarm can be generated to alert that fire 92 is present even if onlysmoke 14 is detected. The device 10 may thus be a fire detection device10 even if it only detects smoke 14, and not fire 92 directly, or if itdetects both smoke 14 and fire 92 directly.

While the present invention has been described in connection withcertain preferred embodiments, it is to be understood that the subjectmatter encompassed by way of the present invention is not to be limitedto those specific embodiments. On the contrary, it is intended for thesubject matter of the invention to include all alternatives,modifications and equivalents as can be included within the spirit andscope of the following claims.

What is claimed:
 1. A fire detection device, comprising: a camera thatcaptures a reference image and a measured image; and a processor thatcompares intensity of the measured image to intensity of the referenceimage and uses this comparison to determine if an alarm is generated toindicate the presence of fire; wherein the intensity of the measuredimage is the total number of photons of the measured image, and whereinthe intensity of the reference image is the total number of photons ofthe reference image.
 2. The fire detection device as set forth in claim1, wherein the camera captures a first reference threshold image and asecond reference threshold image, wherein the processor establishes athreshold based upon a comparison of an intensity that is a total numberof photons of the second reference threshold image to an intensity thatis a total number of photons of the first reference threshold image,wherein the processor determines if a difference between the intensityof the measured image and the intensity of the reference image isgreater than the threshold.
 3. The fire detection device as set forth inclaim 2, wherein the measured image and the second reference thresholdimage are the same image.
 4. The fire detection device as set forth inclaim 1, wherein the processor compares a photon count of eachindividual pixel of the measured image to a photon count of eachcorresponding individual pixel of the reference image and determines howmany of the pixels have a higher photon count in the measured image,wherein the processor compares the number of pixels that have the higherphoton count to a predetermined number and uses this comparison todetermine if the alarm is to be generated.
 5. The fire detection deviceas set forth in claim 4, wherein the processor determines whether thepixels that have the higher photon count in the measured image arecontiguous with one another such that at least fifty percent areimmediately adjacent another one of the pixels that have the higherphoton count, wherein the processor uses this determination to determineif the alarm is to be generated.
 6. The fire detection device as setforth in claim 4, wherein the processor determines whether the pixelsthat have the higher photon count in the measured image are located inan outer area of the measured image that is an area of the measuredimage that includes half of the pixels of the measured image that arefurthest from a center of the measured image, wherein the processor usesthis determination to determine if the alarm is to be generated.
 7. Thefire detection device as set forth in claim 1, wherein the measuredimage and the reference image are black and white images, wherein theprocessor does not use any color images to determine if the alarm isgenerated.
 8. A fire detection device, comprising: a camera thatcaptures a reference image and a measured image; and a processor thatcompares intensity of each pixel of the measured image to intensity ofeach corresponding pixel of the reference image and determines if anintensity difference for each pixel exists that exceeds a thresholdestablished for each particular pixel; wherein the processor determineswhether the number of pixels that exceed their established threshold isgreater than a predetermined number of pixels, wherein the processoruses this determination to determine if an alarm is generated toindicate the presence of fire.
 9. The fire detection device as set forthin claim 8, wherein the intensity of each pixel of the measured image isthe number of photons sensed by that particular pixel of the measuredimage, and wherein the intensity of each pixel of the reference image isthe number of photons sensed by that particular pixel of the referenceimage.
 10. The fire detection device as set forth in claim 8, whereinthe processor determines whether the pixels that have exceeded theirestablished threshold in the measured image are contiguous with oneanother such that at least fifty percent are immediately adjacentanother one of the pixels that have exceeded their establishedthreshold, wherein the processor uses this determination to determine ifthe alarm is to be generated.
 11. The fire detection device as set forthin claim 8, wherein the processor determines whether the pixels thathave exceeded their established threshold in the measured image arelocated in an outer area of the measured image that is an area of themeasured image that includes half of the pixels of the measured imagethat are furthest from a center of the measured image, wherein theprocessor uses this determination to determine if the alarm is to begenerated.
 12. The fire detection device as set forth in claim 8,wherein the threshold established for each individual pixel has an upperlevel that represents a higher number of photons, and wherein thethreshold established for each individual pixel has a lower level thatrepresents a lower number of photons, wherein the intensity differencefor each pixel that exceeds the threshold established for eachparticular pixel is either above the upper level established or belowthe lower level established.
 13. The fire detection device as set forthin claim 8, wherein a detection statistic is determined by the processorfrom an analysis from the group consisting of: (a) a spatial pattern ofthe pixels that exceed the threshold established for each particularpixel; (b) a temporal pattern of pixels that exceed the thresholdestablished for each particular pixel in a series of measured images;and (c) both a spatial pattern of the pixels that exceed the thresholdestablished for each particular pixel, and a temporal pattern of pixelsthat exceed the threshold established for each particular pixel in theseries of measured images.
 14. A fire detection device, comprising: acamera that captures a reference image and a measured image; and aprocessor that identifies pixels of the measured image that are aminority of the pixels of the measured image and that have the highestintensity of the pixels of the measured image; wherein the processorcompares intensity of each of the identified pixels of the measuredimage to intensity of each corresponding pixel of the reference imageand determines if an intensity difference for each of the identifiedpixels exists that exceeds a threshold established for each particularpixel, wherein the processor uses this determination to determine if analarm is generated to indicate the presence of fire.
 15. The firedetection device as set forth in claim 14, wherein the processordetermines whether the number of identified pixels that exceed theirestablished threshold is greater than a predetermined number of pixels,wherein the processor uses this determination to determine if an alarmis generated to indicate the presence of fire.
 16. The fire detectiondevice as set forth in claim 14, wherein the minority of pixels do notexceed 10% of the total pixels of the measured image.
 17. A firedetection device, comprising: a camera that captures a reference imageand a measured image; a light source that emits light that is directedinto a field of view of the camera; and a processor that comparesintensity of the the measured image to intensity of the reference imageand uses an increase in intensity of the measured image from that of thereference image in order to determine if an alarm is generated toindicate the presence of fire, wherein the processor does not use adecrease in intensity of the measured image from that of the referenceimage in order to determine if the alarm is generated to indicate thepresence of the fire.
 18. The fire detection device as set forth inclaim 17, wherein the processor compares intensity of the the measuredimage to intensity of the reference image by comparing intensity of eachpixel of the measured image to intensity of each corresponding pixel ofthe reference image for those pixels in which the intensity of themeasured image is higher than the intensity of each corresponding pixelof the reference image; wherein the intensity of each pixel of themeasured image is the number of photons sensed by that particular pixelof the measured image, and wherein the intensity of each pixel of thereference image is the number of photons sensed by that particular pixelof the reference image.
 19. The fire detection device as set forth inclaim 17, wherein the camera, the light source, and the processor areall components of a smart phone.
 20. The fire detection device as setforth in claim 17, wherein the processor compares the intensity of themeasured image to the intensity of the reference image and determines ifan intensity difference exists that exceeds an established threshold;wherein once the established threshold is exceeded the camera capturesadditional reference images at a rate faster than before the thresholdwas exceeded, wherein the additional reference images are used by theprocessor in order to determine if the alarm is generated to indicatethe presence of fire.
 21. The fire detection device as set forth inclaim 17, wherein the measured image and the reference image are blackand white images, wherein the processor does not use any color images todetermine if the alarm is generated; and further comprising a screenthat displays information about the fire detection device and obtainsinstructions from a user of the fire detection device that arecommunicated to the processor.